Optimization of the electrolytic plasma oxidation processes for corrosion protection of magnesium alloy AM50 using the Taguchi method

A number of studies have been carried out on the use of electrolytic plasma oxidation (EPO) technology for depositing ceramic coatings on magnesium alloys for corrosion protection. However, very few have focused on the optimization of the EPO process parameters. In this study, a design of experiment (DOE) technique, the Taguchi method, has been used to optimize the electrolytic plasma oxidation for the corrosion protection of magnesium alloy AM50. The experimental design consisted of four factors (treatment time, current density, and KOH and NaAlO2 concentrations), with three levels of each factor. Potentiodynamic polarization measurements were conducted to determine the corrosion resistance of the coated samples. An analysis of the mean of signal-to-noise (S/N) ratio indicates that the corrosion resistance of EPO-coated AM50 alloy is influenced significantly by the levels in the Taguchi orthogonal array. The optimized coating parameters for corrosion resistance are 12 min treatment time, 12 A/cm2 current density, 0.9 g/l KOH, 15.0 g/l NaAlO2. The percentage contribution of each factor is determined by the analysis of variance (ANOVA). The results show that the concentration of KOH is the most significant factor affecting the corrosion resistance of the coatings.